1. Field of the Invention
This invention relates to an improvement in an intermittent transmission apparatus for transmitting inputted torque drive as intermittent torque drive.
2. Description of Related Art
A Geneva gear is known as an example of intermittent transmission apparatus for outputting continuous torque drive input as intermittent torque drive. That is, the Geneva gear is capable of alternately producing a drive period in which chive is transmitted to an output shaft, and a non-drive period in which drive is not transmitted to the output shaft.
A conventional and commonly seen Geneva gear, as shown in FIG. 12 has a center portion formed of a driving element D1 and a driven element D2. The driving element D1 includes a member B1 supporting an engaging pin P, and a member B2 having a driving element recess R1 and a circular arc surface S. The driven element D2 includes a member B3 defining four driven element recesses R2 for engaging the engaging pin P and four circular arc recessed surfaces R3 corresponding to said circular arc surface S.
When the driving element D1 rotates, the engaging pin P engages one of the four driven element recesses R2 to rotate the driven element D2 by 90 degrees. At this time, tips of the member B3 of driven element D2 enter the recess R1 provided on the driving element D1, thereby to be allowed to rotate with the driving element D1.
After the 90-degree rotation, the engaging pin P moves out of the recess R2 of driven element D2 while the driving element D1 continues to rotate. Rotation of the driven element D2 is restricted for a fixed period by slidable contact between a recess R3 and the circular arc surface S of driving element D1. This is repeated, whereby continuous rotation of the driving element D1 is transmitted as intermittent rotational motion to the driven element D2.
With such a Geneva gear, when a reactive force is applied from the driven element D2 to the driving element D1 while rotation of the driven element is restricted, this force is received only by the engaging pin P of driving element D1. Thus, it is sometimes inadequate to cope with a strong reactive force only by means of the engaging pin P.
This invention intends to provide improvements over the conventional Geneva gear.
An intermittent transmission apparatus according to this invention also may, broadly, be divided into a driving element and a driven element. The driving element includes a first cam having a first cam surface, a second cam having a second cam surface and a circular arc surface, and an intermediate member having a rotation restricting means. The driven element includes first engaged members for contacting the first cam surface, second engaged members for contacting the second cam surface, and a driven element main body having recesses for contacting the rotation restricting means.
In the intermittent transmission apparatus according to this invention, during non-drive periods of the driven element, the recesses of the driven element main body contact the rotation restricting means provided on the intermediate member of the driving element, in addition to the second engaged members contacting the circular arc surface of the second cam. Thus, during the non-drive periods, rotation is restricted by two methods, and even when a reactive force acts on the driven element, a strong reactive force may be dealt with sufficiently.
Torque drive is transmitted from the driving element to the driven element through the cam surfaces. By varying the shapes of the cam surfaces, a desired profile of output rotating angle may be obtained.